EN31-535A99 SS is an advanced and high carbon chromium-molybdenum alloy steel offering a high degree of compressive strength and abrasion resistance. Best suitable for machined components subjected to abrasive wear, swaging dies, press tools, roller bearings which do not merit a more complex quality. However, its machining is one of the challenging fields in the metal cutting industries due to the high hardness which results in low productivity and high manufacturing cost. In this paper a new interchangeable two phases straight cemented tungsten carbide-cobalt mixed (WC-Co) insert grade (CSTC-K20) tool has been introduced to obtain the optimal turning parameters for the multi-performance characteristics in the turning process by Taguchi coupled grey relational analysis. The flank wear (V bc) and surface finish (R a) were considered as the performance characteristics while the cutting speed (V), feed rate (F) and depth of cut (D) as the controllable process parameters. Experiments were planned as per Taguchi L16 orthogonal array taking three process parameters at four levels. The results revealed that the optimal parametric settings for multi-response becomes cutting speed of 75 m/min, feed rate of 0.05 mm/tooth and depth of cut as 0.25 mm respectively. At this stage the surface roughness (Ra) reduced from 0.132 to 0.061 µm while tool flank wear (VBc) reduced from 0.89 to 0.69 mm and the grey relational grade enhanced up to 0.2867. The polynomial regression model presented higher R 2 value as compared to linear regression model. It is recommended that metal cutting industries could use these optimum approaches to reduce the material waste, manufacturing cost and increase productivity while machining of EN31-535A99 SS.